jcb 3C II head gasket replacement

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osubob24
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jcb 3C II head gasket replacement

Post #1 by osubob24 » Sat Oct 20, 2012 1:52 am

I've bought a JCP 3C II this spring. It would only run for an hour or so before stalling. I pressurized the radiator and I noticed coolant coming from around the head bolts. I guess I'll need to replace the head gasket, a task I've never attempted. Are there any tricks?

Do I need to remove the exhaust manifold? Those bolts look so rusted!

Any help would be appreciated.

Bob


Julian
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Re: jcb 3C II head gasket replacement

Post #2 by Julian » Sat Oct 20, 2012 7:31 am

osubob24 wrote:
Do I need to remove the exhaust manifold? Those bolts look so rusted!



Bob


I've no JCB experience, but in general terms if you don't fancy your chances with the exhaust manifold then it can stay on provided there's room and you can cope with the extra weight.

You'll probably find they do come off though. Give them a wire brushing and soaking in WD40 and use a 6 sided socket on them....

Julian.


essexpete
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Re: jcb 3C II head gasket replacement

Post #3 by essexpete » Sat Oct 20, 2012 6:55 pm

I would agree with Julian, I am sure I have taken head off in the past with out removing manifolds or injectors. That would be the quickest method but I have also replaced a 4.98 and an IH head gasket to find they blew again and the head needed skimming. The other thing I would check is how clean the rad is both with a flush and make sure the external core is not blocked. It is hard to see when the rad is insitu and if there is an oil cooler in front. It may be an old over heating issue that caused head g failure.


philwheelton
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Re: jcb 3C II head gasket replacement

Post #4 by philwheelton » Sat Oct 20, 2012 8:58 pm

The heads are fairly easy to remove with both manifolds on you might need a hand to lift it off as they tend to jam on the studs make sure to undo the oil feed to the rockers it is under the exhaust manifold up the side of the block , head bolts are 100LBS ft valves are 13 thou cold in & out.


Topic author
osubob24
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Re: jcb 3C II head gasket replacement

Post #5 by osubob24 » Mon Oct 22, 2012 5:22 am

How do I check to see if the external core of the radiator is not blocked?
Before I detected the bad head gasket (or head I am not sure), the engine would only run for an hour or so then it would die. It did this 3 or 4 times. So I guess it could be that the engine was overheating. I've never checked a cooling system before. I am lost. Where do I start?

In an attempt to start the engine before I diagnosed the bad head gasket, a friend tried using starter fluid in the air intake. It did not start but the engine did fire and burn only the ether. I think that only made the head gasket problem worse.
I do appreciate the help.
Bob


Julian
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Re: jcb 3C II head gasket replacement

Post #6 by Julian » Mon Oct 22, 2012 11:32 am

osubob24 wrote:How do I check to see if the external core of the radiator is not blocked?
Before I detected the bad head gasket (or head I am not sure), the engine would only run for an hour or so then it would die. It did this 3 or 4 times. So I guess it could be that the engine was overheating. I've never checked a cooling system before. I am lost. Where do I start?

In an attempt to start the engine before I diagnosed the bad head gasket, a friend tried using starter fluid in the air intake. It did not start but the engine did fire and burn only the ether. I think that only made the head gasket problem worse.
I do appreciate the help.
Bob


I'm a little worried here. You ask how to check the external core of a radiator (Mk1 eyeball :-) ) you 'guess' the engine was overheating and you ask advice on how to check a cooling system...... These are all fairly trivial tasks, yet somehow you've managed to diagnose a 'bad' head gasket - something that requires a little more experience. My advice would be to get a second opinion on things before proceeding in at the deep end, the fact the engine dies after an hour is more likely to be a simple fuel blockage.....

Julian.


Topic author
osubob24
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Re: jcb 3C II head gasket replacement

Post #7 by osubob24 » Sat Oct 27, 2012 9:18 pm

Julian,

I started investigating the possible fuel issue first. I removed the injector line on the cylinder closest to the cab, while my father in law was turning it over. I was checking to verify we had fuel going into the cylinders. It started and ran on 3 cylinders, but as I was reinstalling the inj. line I notice a green liquid on top of the engine, which I believe was coolant.
We repeated the process the next day and when the engine started on three cylinders the open injection port spit out coolant! I then pressurized the radiator and coolant came out from the head nuts.

I pretty sure the head gasket it bad. Based on your good advice and experience, I will remove the radiator and flush it to be sure coolant flows freely.
I plan to use PB Blaster to help remove the bolts to the exhaust manifold. I want to finish the welding job on the muffler anyway.

Bob


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Re: jcb 3C II head gasket replacement

Post #8 by philwheelton » Sat Oct 27, 2012 11:59 pm

the injectors have copper sleeves in the cylinder head they can leak around them, if they are leaking you need new sleeves and they are rolled in,some of the later ones have "O" rings around the top of them


Julian
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Re: jcb 3C II head gasket replacement

Post #9 by Julian » Sun Oct 28, 2012 7:54 am

osubob24 wrote: I then pressurized the radiator and coolant came out from the head nuts.



Have you had a spanner on the nuts - check to see if they're all tight.

Julian.


CHM123
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Re: jcb 3C II head gasket replacement

Post #10 by CHM123 » Thu Nov 01, 2012 10:02 am

Morning just joined this site recently and was more or less looking for similar stories to my own, just to see how everyone else did things. Again bought a JCB 3C MkII which didn't have any coolant leeks, but did find the engine hard to start and very smoky, oil in the exhaust etc.
I got brave and removed the head, relatively easy I though, though did remove all the various bits first to make it lighter, can't see why you could not remove it with the exhaust manifold in place, apart from the weight and handling it.
Anyway, replaced the rings and head gasket, but no better!! - so moved on to the head, on the basis the valve stem seals/slides needed to be replaced, but before I got that far took a dislike :( to the engine as I'd no shed and was working in the wet & cold of winter, so replaced it with a nice second hand 4.5 litre John Deere unit. Ok not in keeping with maintaining classic machines, but as I like both a ’76 JCB & ’76 John Deere, now my backhoe is simply "JCDeere."
I'm by no means an expert, but base on my fun to date it sounds your issue are all in the engine head, if lucky skimmed, seals and gasket, etc, if unlucky, replacement head. I've attached a photo of where you'll probably be in the near future, if not already. Be interested to hear how you got on, or if you have any practical questions I may be able to help with. I got a copy of the engine manual which was a great help in the whole process.
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